Process of working clad metals.



W. M. PAGE & W. TASSIN.

PROCESS OF WORKING GLAD METALS.

APPLICATION FILED APILZB, 1910.

1 1 7 1 ,637 w Patented Feb. 15, 1916.

3 SHEETSSHEET I.

' amwfito'cs wane/was w M p w LA TZS s W. M. PAGE & W. TASSIN.

PROCESS OF WORKING CLAD METALS.

APPLICATION FILED APR. 28. 1910.

Patented Feb. 15, 1916.

3 SHEETSSHEET 2.

Witmmoao W. M. PAGE & W. TASSlN.

PROCESS OF WORKING CLAD METALS.

APPLICATION FILED APR.28, 1910.

Patented Feb. 15, 1916.

SSHEETS-SHEET 3.

@fvitmeoaaa UNITED STATES PATENT WILLIAM MARSHALL PAGE, OF PHILADELPHIA, AND WIR'I. TASSIN, OF CHESTER, PENNSYLVANIA, ASSIGNOBS, BY MESNE ASSIGNMENTS, TO DUPLEX METALLIC COMPANY, A'CORPORATION OF PENNSYLVANIA.

rnocnss or WORKING GLAD METALS.

Specification of Letters Patent.

Patented Feb. 15, 1916.

1 '0 all wh'om it may concern Be it known that we, WILLIAM MARSHALL PAGE and Wm'r TAssIN, citizens of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, and Chester, in the county of Delaware and State of Pennsylvania, respectively, have invented certain new and useful Improvements in Processesof VVork- "ing Clad Metals, of which the following case of copper-clad steel, 2. high tensile strength as a whole, a good degree of purity in each of the joined metals and an improvement in the character of the metal along the line of weld together with preservance of such weld; all as more fully hereinafter set forth and 'as claimed.

Steel coated permanently and integrally united,"o'r weld united, with copper has recently become commercially available (Patents 853,716 and 893,932). Such material, known as copper clad steel, may be worked by rolling, drawing, swaging, etc., in much the same manner as a similar article of a single metal. Copper clad steel is particularly advantageous for electrical conductors as combining strength and conductivity.

There are certain points however in which the copper-clad wire hitherto made is susceptible of improvement. Its conductivity is often not as great as it should be, being rather less than that which should be due to the sectional area of the copper present without considering the steel core, andits quality is apt to be irregular, both in this respect and in respect to its strength.

It is the purpose of the present invention to improve the copper-clad metal in these respects and to produce wire and rod' having still greater tensile strength, limit of elasticity and conductivity, producing a compound conductor'having a greater tensile strength and elastic limit than that normal to the steel of the core worked under ordinary conditions and also having a greater conductivity than that corresponding to the amount of copper present.

Although by the methods now in use in producing clad steel billets some improvement in the quality of the steel of the core is, or may be, effected, yet necessarily but little atte'ntioncan be paid to this point during the coating operation, the production of the weld-union being then of course the main consideration. In forming the weld-union, furthermore, more or less mixing or alloying of the steel and copper along the line of unlon necessarily takes place and to this extent the conductivity of the joined metals is impaired copper alloys having a relatively low conductivity. The extent of the alloying is not great in good-quality clad-steel, nor does it extend far into the metals on either side, the joining layer or film of mixed metals being of little thickness. Still these alloyed layers are present and must be taken into account.

When copper clad metal is worked down by ordinary methods of rolling, the final product can be much improved by a heat treatment. By heating the finished wire rod or-bars to about 1250 F. for a relatively long time and allowing to cool rather slowly, the quality of the steel is raised while the conductivity of the material as a whole is also improved, this last result being due to the influence of the heat upon the copper-iron alloys present between the copper and the steel, long continued heating changing the character of these alloys materially. In lieu of presentingacoarsely crystallized character by this treatment they become finely crystalline and there is a molecular change, possibly adding somewhat to the pure-copper area and also perfecting the weld somewhat. At all events, in operating in this manner and subsequently working down the treated wire rod to wire a conductor of higher tensile strength and higher conductivity is obtained.

In one embodiment of the present invention therefore, the clad metal billets may be simply rolled down to wire rods or bars in the ordinary steel-working methods and with the ordinary apparatus, the product heat-treated as described and the bars drawn .down to wire in the ordinary manner. Bet- 1 as to finish at a good full red. The finishing temperature should be between 1300 F. and 1850 F. .A. temperature of 1300 F. is advantageous. For rolling rolls having bluntedged oval grooves are employed and the metal is looped as frequently as possible. With grooves of this form rapid work can be performed without the danger of forming a fin of copper having a sharp angle which in a subsequent rounding pass may be folded over in lieu of being forced down into the body of the copper, thereby producing a lap which will persist through subsequent rolling and give a longitudinal seam in the finished article. With the rapid work required in the present invention, blunt edged grooves should be used, thereby enabling frequent looping. For example, by

-using the 12-inch and 10-inch looping mill the reduction from a four inch billet carrying, say, 40 per cent. of copper down to a =3 inch rod may be made in 15 passes. The initial temperature is advantageously as high as it can be raised without melting off the copper; say about 1000 C. or 1800F. or just below the melting point of copper. The preliminary heating of the compound billets should endure long enough to cause a substantially uniform penetration of the heat or in other words, there should be a good soaking heat. The heating should, however, not be longer than is necessary to produce this uniform high temperature throughout the billet since otherwise the physical properties of the metal are apt to suffer. Rolling should be rapid enough to deliver the finished rod at a heat which is at least a good rod heat. Working in the manner indicated a number of advantageous alterations take place in the quality and character of the clad metal. The steel is very much improved in quality and strength and the surrounding layers of iron-copper alloy are changed materially in a manner raising their conductivity, and therefore that of the compound metal as a whole.

The improvement in conductivity in a wire produced by working the clad metal according to the present invention as compared with a wire produced from the same metal by the ordinary rolling and drawing operations is always very great and the improvements in strength'and standardization are also noteworthy. An ordinary copper clad wire having 40 per cent. of its section copper and 60 per cent. steel may often have a conductivity of only 35 per cent. of that of a solid copper wire of the same gage. The

reduction in conductivity is probably due method of rolling, its other properties may.

also be improved, giving a product of very good tensile strength and more uniform character. The physical character of the core steel becomes quite unlike that of naked steel worked down in the ordinary way to a similar stage of reduction.

By hot rolling copper-clad billets in the described manner and under the described conditions, not only is the conductivity improved but a singularly great improvement is made in the strength of the wire rod as a whole; and this improvement, with care in subsequentdrawing operations, is retained in the wire finally produced. The improvement in the uniformity of the material is also remarkable, one coil of wire being like another as regards conductivity, strength, elastic limit, etc. The copper-clad inch rod so produced has a tensile strength which is greater than that which would be expected from the sum of the strengths of the copper and of the steel present. The strength of the copper-clad rod is indeed greater than could ordinarily be produced in a naked steel rod of the same. steel as the core and of the same diameter as the copperclad .rod run through the same process of treatment, and is markedly greater than the strength of a. rod of the same diameter as the core. In making copper-clad billets, low carbon steels are ordinarily used for the core because of their relatively high conductivity; but the wire rods made from copperclad metal having a core of low carbon steel have a tensile strength which is greater than that of many like-diameter rods made of what are ordinarily considered strong steels, though only 60 per cent. of the sectional area of the copper-clad wire rod is steel. There are special steels which are stronger, but these steels are hardly comparable since they are high-carbon material with high ohmic resistance and not well suited for conductors. But by their use with the copperclad metal, the tensile strength can be still further raised. However, for the present purposes only the low-carbon steels. will be considered.

In copper-clad wire produced under the present invention are combined a high conductivity together with a high tensile strength; the combination being such as cannot be found in the present types of com mercial conductor wire. For example, a No. 10 copper-clad low-carbon steel wire under the present invention carrying 40 per cent. of copper and 60 per cent. of steel will exhibit a breaking weight of 87 0 pounds, or 100,000 pounds per square inch while the nearest comparable conductor wire carrying a protective coating, a No. 10, galvanlzed all-steel wire of like steel may exhibit only about 611 pounds breaking Weight, or 75,000

pounds per square inch with a conductivity, elastic limit and resistance to weather which are much less. The best naked iron or steel electrical conductor wires now on the markets, such as the grades known as 13.13.13. and RB, have a tensile strength and of course, conductivity muchbelow that of the copper-clad metal produced in the despribed manner. No. 10 EBB. wire, for instance has a breaking Weight of about 495 ppunds with a tensile strength of about 60,000 pounds while B.B. (which has a less conductive value) has a breaking weight of about 545 with 65,500 tensile strength.

Another illustration of the advantageous character of the present conductor may be made by comparing the properties of two similarly protected wires containing the same steel. A double-dipped galvanized steel wire of 0.162 inches diameter made under ordinary conditions, may, for instance, have a breaking weight of 1406 pounds with an ohmic resistance of 17 .0 per mile while the same steel given a 40 per cent. coating of copper and drawn into wire of the same size, that is, 0.162 inches, under the described conditions may have a breaking weight of 1874 pounds with an ohmic resistance of but 5.11 per mile; and yet this last wire has 40 per cent. less sectional area of steel. It has a third greater strength with less than a third the resistance.

Still another comparison may be given by tabulating the properties of the best present commercial all-steel conductors and those of the present conductor.

The conductors, BB. and E.B.B. are special commercial grades intended to give the least resistance for the greatest strength possible. And yet the new conductor transcends both in both regards. These comparisons are of course only of the conductor wires as they come on the market.

In the accompanying illustration, We have reproduced more or less diagrammatically, certain characteristic appearances of the metal as viewed in section under the microscope, certain views of this illustration being reproduced from the original photomicrographs. In this showing all the metal sections represent the same polishing, etching and magnification.

Figures 1 and 2 represent respectively longitudinal and cross-sections of the original steel billets used for coating; Fig. 3 is a longitudinal section of the same steel after applying the copper coating, showing the effect of the coating operation; Fig. 4 is a cross-section of the steel of a clad billet rolled to i-Heths inch rod in the usual way; Fig. 5 is a similar section across'the line of joinder between steel and copper showing the intervening and linking alloy film; Figs. 6 and 7 are respectively cross and longitudinal sections-of the same steel when rolled bare to inch rod; Figs. 8 and 9 are respectively cross and longitudinal sections of the same steel clad with copper and rolled to =3 inch rod under the present invention and showing the comparative uniformity of character of the steel; Fig. 10 is a longitudinal section of the same rod taken across the line of union; Fig. 11 is a longitudinal section in the steel of a copper clad wire under the present invention; Fig. 12 is a and Fig. 13 is a similar view with the rolls in a vertical oval ass.

In Figs. 1 and 2, the various light and dark areas represent various different components of the steel billet used in making the copper clad metal, the magnification being about 270 diameters.

In Fig. 3 the same steel is shown after the application of a copper coating to it. It will be noted that the texture is, comparatively finer, the heating incident to the coating operation having changed the quality'of the steel.

In Fig. 4 the steel of the same coated metal is shown as it is after rolling to rod; and it will be noted that there is a marked improvement in the character'of the steel.

In Fig. 5 is shown a section of the same rod taken across the line of union. The

grained area is steel and the more uniform appearing area is copper while the intervening black area is a layer of copper-iron alloy.

. In Figs. 6 and 7 are shown views of the same steel rolled naked in the same way. It Will be observed that though the size of the grains is reduced, incharacter the metal is about the same as the original steel (see Figs. 1 and 2) but is different from the same steel worked in the same way as a core for a copper-clad rod (see Figs. 4 and 5). The size of grain in the bare steel 3-inch rod, is but a. little smaller than the size of the grain in the 34% inch copper-clad billet, and since the physical properties of the steel, other things being equal, is indicated by the fine ness of grain, the comparison is at once obvious.

In Figs. 8 and 9, on the other hand, are shown a section of the core steel of the new conductor of the present invention. It will be noted that the grain has become so exceedingly fine that the structure is ractically irresolvable at this power (magni cation 270 diam), the metal aving a practically homogeneous aspect. The difierenc'e shown in the drawing and in the photographs, is merely a light-and-shade surface differentiation with a few specks here and there. The same fine-grained structure is shown in Fig. 11 which is a section of a wire drawn down from the rod of Figs. 8 and 9.

In the showing of Fig. 10, which is taken across the union, it will be noted that the steel area (at the top of the view) is almost as structureless as the copper area as shown, offering a wide contrast with the steel of the compound metal of Fig. 5 which represents the former art. It will also be noted that there is a blackish area next the copper. composed of a high copper alloy, a lightish area next the steel, composed of a high iron alloy and grayish streaks of another alloy between them. There appear to be at least three alloys present; and may be more.

In the showin of Fig. 12, element 1 is a pair of rolls (5 own broken away), provided with horizontal oval grooves 2 containing a clad metal billet or rod, 3 representing the .steel core and 5 the copper sheath. The showing in 13 is the same save that the grooves are vertical. It will be noted" in both showings the edge of the groove is rounded away causing any copper which may ear out, as at 4 to assume a form readily permitting it to sink back into the main body upon further rolling in a reverse pass. In rapid rolling, such as is contemplated under the present invention. the copper extends more or less laterally and where the groove is provided with a sharp' corner or arris, this lateral extension is given a sharp angle at the point where it joins the main body of the coating. With an angle at this point, in the next pass the copper projection or fin is apt to fold over instead of being merely compressed back into the body of the copper coating, and this fold, once formed, does not disappear in subsequent rolling so that in the finished article there may be a longitudinal seam or crevice at the point of lap. This danger with sharpcornered grooves is particularly great where, as in the present invention, the copper clad metal is worked at a maximum speed in order to secure a high-temperature reduction throughout. With the oval grooves, more over, the rounded shape of the core is preserved throughout and there is much less difliculty in preserving its centering with regards to the copper coat.

To recapitulate, in the embodiment of the process at present preferred, the copper clad billet after the coating operation is given a preliminary rolling, as through a pair of roughing rolls, being reheated if necessary. The extension given in this preliminary rolling operation should not be great, as it serves mainly to compact the coating, obviating porosities. After this preliminary working, the billet may be placed in a furnace of suitable type, such as a mufile furnace, and heated to a point just short of the melting point of copper. It is desirable to get the heat uniform throughout the billet and as near this point as possible. The desired temperature of the metal is indicated in practice by a particular appearance which, in the factory, is sometimes termed a 'blick. After thus heating, the compound billet is passed through rolls having.

an oval section and worked down to wire rod as rapidly as possible.

What we claim is 1. The process of producing a strong, highly conductive clad metal conductor which comprises rolling down a clad metal billet 'to wire rod size and allowing the extended article to cool slowly from a temperature above 1300 F.

2. The process of producing a strong, highly conductive metal conductor which comprises rolling a copper-clad billet to final shape and wire rod size within a range of temperatures between 1800 F. and 1300 F. and allowing the finished metal to cool slowly from a temperature above 1300 F.

3. The process of producing a strong, highly conductive metal conductor which comprises heating a copper clad billet to a temperature just below the melting point of copper and finishing to wire rod at a temperature about 1300 F.

4. The process of producing a strong, highly conductive metal conductor which comprises rolling a copper clad billet through blunt-edged oval passes to wire rod size, the temperature during the rolling operation being maintained between 1800 F. and 1300 F. and finishing at a temperature above 1300 F.

5. The process of producing a strong, highly conductive metal conductor which comprises heating a copper clad billet nearly to the melting point of copper, rolling the same through blunt-edged oval grooves with repeated looping to a wire rod size and during the rolling operation maintaining the temperature above 1300 F.

In testimony whereof, we afiix our signatures in the presence of witnesses.

WILLIAM MARSHALL PAGE. VVIRT TASSIN. Witnesses:

C. M. WEIS, JOHN B. POTTER. 

